This function will copy a public key object into a PKCS 11 token specified by a URL. Valid flags to mark the key: GNUTLS_PKCS11_OBJ_FLAG_MARK_TRUSTED, GNUTLS_PKCS11_OBJ_FLAG_MARK_SENSITIVE, GNUTLS_PKCS11_OBJ_FLAG_MARK_PRIVATE, GNUTLS_PKCS11_OBJ_FLAG_MARK_CA, GNUTLS_PKCS11_OBJ_FLAG_MARK_ALWAYS_AUTH.